Hey @Lakshan,
If you have a process with just Service Tasks and all are implemented as Java Delegates you won’t see an active instance in Cockpit because it will already be passed through. So there is basically no active instance and just history.
If you like to observe the state you could add a user task. Once the instance arrives there it will be visible in Cockpit.
There is also a possibility to use a History Plugin built by @datakurre. If you add it to Camunda you will be able to see the History of your process instances that passed through all the service tasks. You can also find a blog post about the plugin and the usage and installation.
I hope that solves your problem and makes the instance visible for you in Cockpit.
Cheers
Nele